#include <stdio.h>
#define PI 3.142
main()/*这是用宏定义‘#define’求圆面积的程序，对应可执行文件1-3 */
{
float r , squ ;
printf("input the 'r' of a circle\n");
scanf("%f",&r);
squ=PI*r*r;
printf("the squ of the circle is :%-12.5f\n",squ);
printf("\n");
}

